Solar energy collectors are well known in the art, but the present invention is directed to an inexpensive and simplified structure wherein a continuous shaped film provides parabolic reflective surfaces and heat-absorbing conduits. The film is supported by shaped support surfaces which not only hold the film in place but also conform to the shape of the underside of the parabolic reflectors and wherein the shaped support surfaces have structural rigidity provided by a bottom support of inexpensive construction.
The present application more clearly describes the structure originally shown in the parent application, Ser. No. 886,217. Furthermore, it distinguishes over the art of record in that case and the references cited during the prosecution of that application.
Early disclosures illustrate parabolic reflectors and heat absorbers, but the prior art fails to teach how to make the parabolic reflectors and the heat absorbers from a continuous sheet or film.
U.S. Pat. No. 4,120,283 of Eder, and U.S. Pat. No. 3,129,703 of Tabor show the use of foil--in Eder as a matrix of zig-zag folds, but without conduits or reflectors, and Tabor without reflective surfaces. Neither suggests the use of foil for a purpose other than absorption.
U.S. Pat. No. 4,150,657 of Bowen shows a flat plate collector formed from heavy gauge metal to provide "annular" conduits at spaced intervals, and subsequently, welded. There is no suggestion that foil could be used, nor that the continuous piece could be shaped into a focusing reflector.
West Germany Pat. No. 2,546,619 of Antonioli shows metal shaped in corrugated fashion, but the corrugations are arranged to yield functional results of a non-concentrating (full absorber) panel. There is no teaching of a reflective surface, central absorber, nor concentrating effect.
U.S. Pat. No. 4,131,109 of Coxon deals with a collector that is not a full absorber type, nor a full concentrating type. Coxon lacks a fluid channel in the central absorber, cannot restrict and contain fluids for ordered flow, and cannot be folded from a common piece of material. Further Coxon cannot be made from foil because it lacks underlying supports.
U.S. Pat. No. 3,321,012 of Hervey and U.S. Pat. No. 4,099,516 of Caulier do not teach the use of light-gauge foil for forming the reflector. Caulier also distinguishes over reflector plate material and foil used to reflectively cover the end plates (4A and 4B).
In both Hervey and Caulier, a member is interspersed between the absorber and the reflector surface, said member precluding the use of a common web or piece of material to form three sides of the absorber conduit.
In each case, the absorber pieces (15 of Hervey, 2 of Caulier) are distinctly identified as separate entities. Neither patent suggests or identifies the use of lightweight non-rigid materials to form the reflector.
U.S. Pat. No. 3,982,527 of Cheng is directed to a vertically extended heat branch with a small absorption coated heat sink to absorb concentrated focused solar rays. However, the heat must be conductively transferred to a heat transfer fluid contained in conduits behind the panel. In other embodiments, the parabolic shaped surface and absorber are both absorptively coated. Cheng does not teach the use of an enclosed absorber conduit in the central focal region and does not suggest or use foil.
In U.S. Pat. No. 4,024,852 of L'Esperance (and especially in FIG. 10), the substrate 63 is merely a "base" for a formed reflector shape 64 or a thin film 64 placed on top of a trough-like plastic foam shape. This second embodiment is no different from U.S. Pat. No. 3,847,136 of Salvail which also teaches the use of a full trough support with reflective foil inside the trough. Salvail's teaching was available to L'Esperance, but he--like all others before--failed to see that the reflective film could be shaped into a form that permits the beneficial results of integral vertically extended absorber.
L'Esperance teaches the use of a solid plate absorber (25) without internal fluid channels and, like Cheng, must depend on a horizontal, substantially extended conductive path to transfer heat to external fluid means. There is no suggestion of using foil in this special relationship of L'Esperance.
Although French Pat. No. 2,304,875 of Pinon and West German Pat. No. 2,643,431 of Swisspor AG suggest a focusing collector absorber and reflector made from the same piece of material, they can be distinguished over the present invention.
Swisspor AG uses a vertical extension of the reflector to support an independent conduit, but an upper part of said extension could also absorb heat. On the opposite co-acting side of the reflector, Swisspor AG chooses to terminate plate 25 adjacent the nadir of the reflector. Swisspor AG also lacks a cooperating under-support, even though Salvail's teaching was available, but went unrecognized. It is obvious that heavier gauge sheet material is used in Swisspor and that the extension 23 curves primarily as a support for conduit 21 (which is (are) curved and unsupported at the ends) 22--see FIG. 3.
Although Pinon suggests the construction of a reflector and absorber from a common piece of material, it does not teach the importance of a cooperating undersupport as being necessary for the use of thin gauge materials like foil and selectively coated thin films, etc.
Lacking the necessary undersupport, Pinon obtains structural integrity by extending the base material (plastic across the top)but, by so doing, imposes other limitations:
(a) Pinon is limited to the use of transparent plastic in order to let solar rays penetrate the top cover,
(b) by making the reflector-absorber-cover as an integral and completely self-contained unit, Pinon precludes the advantageous use of "folding" and high-speed production techniques since he is forced to extrude the integral assemblies in the direction of the conduit.